Anti-ultraviolet film of immobilized anthocyanin as well as preparation method and application of anti-ultraviolet film

Abstract

The invention discloses an anti-ultraviolet film of immobilized anthocyanin as well as a preparation method and application of the anti-ultraviolet film. The method comprises the following steps: adding anthocyanin and a coupling agent into a polyvinylamine-co-hydroxyethyl methacrylate (2) copolymer solution to obtain a blended solution; carrying out heating reaction on the blended solution, and adding a reaction product into a non-solvent phase to separate out a solid product; drying the solid product, and dissolving in water to obtain a membrane casting solution; and carrying out film coating treatment on the film casting solution, and drying to obtain the anti-ultraviolet film containing the immobilized anthocyanin. The prepared anti-ultraviolet film containing the immobilized anthocyanin is applied to the packaging field of food, medicine and the like. The anti-ultraviolet film containing the immobilized anthocyanin prepared by the method can realize the immobilization of the anthocyanin in a packaging film material, effectively block ultraviolet rays, and avoid article pollution caused by loss of the anthocyanin in a packaging and using process; meanwhile, the gas barrier property of the anti-ultraviolet film is improved, and the storage life of food is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of functional membrane technology, specifically relating to an immobilized anthocyanin UV-protective film, its preparation method, and its application. Background Technology

[0002] Food is susceptible to spoilage due to microbial contamination during processing, storage, transportation, and consumption. Polymer films are commonly used packaging materials for food and pharmaceuticals, and the modern food industry has placed demands on functional upgrades to packaging films. Traditional polymer packaging films have limited functionality and cannot solve the problem of food spoilage. Furthermore, simple packaging is no longer sufficient to meet the modern food industry's requirements for "long shelf life, cross-regional distribution, and additive-free preservation."

[0003] Currently, functional upgrades of packaging films are mainly achieved by combining functional factors with substrates through physical, chemical, and biological methods. Adding anthocyanins to the film material is a common upgrade method. Other technologies utilize electrostatic complexation and hydrogen bonding through macrocyclic chemistry such as cyclodextrins to immobilize anthocyanins and address their susceptibility to degradation and dissolution. Film materials prepared using simple physical doping methods may fail due to anthocyanin migration, loss, and aging, and may also contaminate packaged goods. While methods like electrostatic complexation and hydrogen bonding using macrocyclic chemistry such as cyclodextrins to immobilize anthocyanins address degradation and dissolution, these methods are susceptible to the effects of storage environments. Traditional simple packaging can no longer meet the demands of modern food industries for long shelf life, cross-regional distribution, and additive-free preservation, prompting a shift towards functional upgrades in packaging films, focusing on high barrier properties, antibacterial properties, and antioxidant properties. Summary of the Invention

[0004] To address the issues of easy degradation and leaching in existing packaging film materials modified with anthocyanins, which fail to meet the preservation and functional requirements of modern food industries, this invention provides an immobilized anthocyanin UV-protective film, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing an immobilized anthocyanin UV-protective film, comprising the following steps: Anthocyanins and a binder were added to a solution of polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer to obtain a blend solution; The blend solution is heated to react, and the reaction product is added to a non-solvent phase to precipitate a solid product; The solid product is dried and then dissolved in water to obtain a casting solution. The casting solution was coated and dried to obtain a UV-protective film containing immobilized anthocyanins.

[0006] Furthermore, the mass ratio of the polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer, anthocyanin and binder is 20:(0.1~0.5):(2~5).

[0007] Furthermore, the temperature at which the blend solution is heated is 80℃~120℃.

[0008] Furthermore, the binder includes one or more of 1,2-dichloroethane, 1,2-dibromoethane, 1,2-difluoroethane, 1,3-dichloropropane, 1,3-dibromopropane, 1,3-difluoropropane, 1,4-dichlorobutane, 1,4-dibromobutane, or 1,4-difluorobutane.

[0009] Furthermore, the non-solvent phase is one of methanol, diethyl ether, or acetone.

[0010] Furthermore, the concentration of the casting solution is 2% to 15%.

[0011] Furthermore, the drying temperature of the solid product is 60~100℃; the drying temperature of the casting solution after coating treatment is 50~100℃.

[0012] The present invention also provides an immobilized anthocyanin UV-protective film, which is prepared according to the above-described method for preparing an immobilized anthocyanin UV-protective film.

[0013] Furthermore, the thickness of the UV-protective film is 3~300um.

[0014] The present invention also provides the application of the above-mentioned UV-protective film containing immobilized anthocyanins in the packaging of food and medicine.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method provided by this invention uses polyethyleneimine common The 2-hydroxyethyl methacrylate copolymer is used as the film-forming matrix. Anthocyanins and a binder are introduced into the copolymer solution to form a blend system. The anthocyanins are then heated to achieve covalent bonding between the anthocyanins and the matrix. The process route of non-solvent phase precipitation and drying to form a film is simple to operate, mild, and easy to implement on a large scale. This preparation process can achieve uniform dispersion and stable fixation of anthocyanins in the polymer matrix, avoiding the phase separation and agglomeration problems that are easy to occur in physical blending. At the same time, the reaction conditions are mild and easy to apply in industrial applications.

[0016] The UV-protective film containing immobilized anthocyanins obtained by this invention stably binds anthocyanins to the copolymer matrix through covalent bonds, which can significantly inhibit the dissolution and loss of anthocyanins during use, greatly improving the long-term stability and service life of the film. Relying on the covalent connection between anthocyanins and film-forming agents to construct a dense internal structure of the film, it endows the material with excellent gas barrier properties. At the same time, it achieves efficient UV blocking by utilizing the UV absorption characteristics of anthocyanins themselves, which can effectively reduce the temperature inside the film. Moreover, the color-changing characteristics of anthocyanins are preserved, so that the film also has a visual response function.

[0017] The UV-protective film containing immobilized anthocyanins obtained in this invention can be applied in the fields of food and pharmaceutical packaging and storage. Its high-efficiency UV blocking and gas barrier properties can delay the oxidation, degradation and deterioration of the contents, and extend the shelf life. The cooling effect brought by UV blocking can reduce the adverse effects of the storage environment on heat-sensitive foods and pharmaceuticals, and improve storage safety. At the same time, the storage quality of food or pharmaceuticals can be detected in real time by visually detecting the color change of anthocyanins. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below: Figure 1 The graph shows the UV blocking rate test results of the UV-protective film containing immobilized anthocyanins prepared in the embodiments of the present invention and the film prepared in the comparative example. Detailed Implementation

[0019] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0020] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0021] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0022] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0023] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0025] Polymer films are widely used in food and pharmaceutical packaging, but they have some significant drawbacks. For example, their function is relatively limited, serving only simple wrapping and isolation purposes, failing to effectively address spoilage issues such as microbial contamination and lipid oxidation during storage and transportation. While existing technologies have proposed various solutions, these methods still have numerous problems and have not completely resolved the industry's pain points. For instance, in functional packaging films prepared using simple physical doping methods, anthocyanins are prone to migration, loss, and aging during use. This not only leads to the failure of the packaging film's function and its inability to preserve freshness but may also cause them to migrate into the packaged food or pharmaceuticals, contaminating the packaged items. Methods for fixing anthocyanins, such as electrostatic complexation and hydrogen bonding mentioned in patents, have poor stability and are easily affected by storage environments (such as temperature and humidity), resulting in inconsistent performance under different conditions. In summary, current technological solutions all have certain limitations and cannot adequately meet the functional requirements of modern food industry packaging films. Developing more stable and effective functional packaging film preparation technologies remains an urgent need for the industry.

[0026] Based on this, the present invention provides a method for preparing an immobilized anthocyanin UV-protective film, comprising the following steps: Anthocyanins and a binder were added to a solution of polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer to obtain a blend solution; The blended solution is heated to react, and then the resulting reaction solution is added to a non-solvent phase to precipitate a solid product; The solid product is dried and then dissolved in water to obtain a casting solution. The casting solution was coated and dried to obtain a UV-protective film containing immobilized anthocyanins.

[0027] In some specific embodiments of the present invention, the mass ratio of the polyethyleneamine-co-methyl methacrylate (2) hydroxyethyl ester copolymer, anthocyanins, and binder is 20:(0.1~0.5):(2~5). An appropriate reaction mass ratio ensures that the anthocyanins and the polyethyleneamine-co-methyl methacrylate (2) hydroxyethyl ester copolymer undergo a sufficient covalent reaction through the binder, thus avoiding excessive anthocyanin aggregation that could affect the film's light transmittance and film-forming properties, and also preventing the anthocyanins from being poorly fixed and easily lost.

[0028] In some specific embodiments of the present invention, the temperature for heating the blend solution is 80°C to 120°C. This temperature reaction can promote the efficient formation of stable covalent bonds between anthocyanins and copolymers by the linker, ensuring the immobilization effect, and can also avoid anthocyanin degradation caused by high temperature.

[0029] In some specific embodiments of the present invention, the linker includes one or more of 1,2-dichloroethane, 1,2-dibromoethane, 1,2-difluoroethane, 1,3-dichloropropane, 1,3-dibromopropane, 1,3-difluoropropane, 1,4-dichlorobutane, 1,4-dibromobutane, or 1,4-difluorobutane. These types of linkers possess suitable reactivity, enabling them to bind the amino groups in the copolymer to the hydroxyl groups in the anthocyanins, achieving covalent bonding and enhancing the stability of anthocyanin fixation.

[0030] In some specific embodiments of the present invention, the non-solvent phase is one of methanol, diethyl ether, or acetone.

[0031] In some specific embodiments of the present invention, the concentration of the casting solution is 2% to 15%. This mass concentration range can balance the fluidity and film-forming properties of the casting solution, and the appropriate concentration can ensure that the coating is smooth and uniform, forming a dense and stable UV-resistant film after drying.

[0032] In some specific embodiments of the present invention, the drying temperature of the solid product is 60~100℃; the drying temperature of the casting solution after coating treatment is 50~100℃.

[0033] The present invention also provides a UV-protective film containing immobilized anthocyanins prepared by the above-mentioned method for preparing a UV-protective film containing immobilized anthocyanins, wherein the film thickness is 3~300 μm; and its application in the packaging of food and medicine.

[0034] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0035] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0036] The preparation method of the polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer used in the following examples is as follows: N-vinylformamide, 2-hydroxyethyl methacrylate, and 2,2'-azobisisobutylamidine dihydrochloride were slowly added to a three-necked flask, controlling the molar ratio of N-vinylformamide to 2-hydroxyethyl methacrylate to be 7:3. The polymerization reaction was carried out under a nitrogen atmosphere and with vigorous stirring. The mixture was refluxed in a 65°C water bath with mechanical stirring to accelerate polymerization. After 4 hours of reaction, a viscous solution was obtained. The resulting mixed solution was then subjected to a 1.0 mol... L - ¹Hydrolysis was performed in hydrochloric acid aqueous solution, and the hydrolysis product was precipitated in methanol and dried under vacuum at 100°C overnight. The dried white crude product was dissolved in deionized water and ion exchanged with an anion exchange resin to obtain a polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer.

[0037] Example 1 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 2g of 1,2-dichloroethane and 0.1g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 80℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to a methanol-sodium hydroxide solution to precipitate. The precipitated solid product was dried at 60℃ and then dissolved in water to obtain a casting solution (mass concentration of 2%). The casting solution was coated onto a glass plate and dried at 60℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 100µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0038] Example 2 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 2g of 1,2-dichloroethane and 0.2g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 100℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to a methanol-sodium hydroxide solution to precipitate. The precipitated solid product was dried at 60℃ and then dissolved in water to obtain a casting solution (mass concentration of 8%). The casting solution was coated onto a glass plate and dried at 100℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 100µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0039] Example 3 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 5g of 1,2-dichloroethane and 0.5g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 120℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to a methanol-sodium hydroxide solution to precipitate. The precipitated solid product was dried at 60℃ and then dissolved in water to obtain a casting solution (mass concentration of 15%). The casting solution was coated onto a glass plate and dried at 80℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 300µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0040] Example 4 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 5g of 1,2-dibromoethane and 0.5g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 80℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to a methanol-sodium hydroxide solution to precipitate. The precipitated solid product was dried at 80℃ and then dissolved in water to obtain a casting solution (mass concentration of 15%). The casting solution was coated onto a glass plate and dried at 50℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 3µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0041] Example 5 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 3g of 1,2-difluoroethane and 0.5g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 80℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to a methanol-sodium hydroxide solution to precipitate. The precipitated solid product was dried at 80℃ and then dissolved in water to obtain a casting solution (mass concentration of 2%). The casting solution was coated onto a glass plate and dried at 100℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 3µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0042] Example 6 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 5g of 1,3-dichloropropane and 0.5g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 100℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to diethyl ether to precipitate. The precipitated solid product was dried at 100℃ and then dissolved in water to obtain a casting solution (mass concentration of 2%). The casting solution was coated onto a glass plate and dried at 50℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 300µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0043] Example 7 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 2g of 1,4-dichlorobutane and 0.2g of anthocyanin were added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution to obtain a blend solution. The blend solution was stirred and heated to 100℃, reacted for 30min, and then cooled. The reaction product was then added dropwise to acetone to precipitate. The precipitated solid product was dried at 100℃ and then dissolved in water to obtain a casting solution (mass concentration of 15%). The casting solution was coated onto a glass plate and dried at 60℃ to obtain a UV-protective film containing immobilized anthocyanin with a thickness of 300µm. The obtained UV-protective film containing immobilized anthocyanin was used for food or pharmaceutical storage.

[0044] Comparative Example 1 50g of polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer was dissolved in water to obtain a casting solution; the casting solution was coated onto a glass plate and dried at 60°C to obtain a film with a thickness of 3µm. The film was then used for the storage of food or medicine.

[0045] Comparative Example 2 20g of polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer was dissolved in water to obtain a polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution. 0.2g of anthocyanin was added to the polyvinylamine-co-methyl methacrylate (2-hydroxyethyl ester) copolymer solution, and the mixture was stirred and cooled to obtain a casting solution. The casting solution was coated onto a glass plate and dried at 60°C to obtain a film with a thickness of 300µm. The prepared film was used for food or pharmaceutical storage.

[0046] The thin films prepared in the above embodiments and comparative examples were tested for relevant properties, and the test results are as follows: The gas barrier properties of the UV-protective films containing immobilized anthocyanins prepared in Examples 1-7 and the films prepared in Comparative Examples 1-2 were tested using a permeameter apparatus, and the results are shown in Table 1. As can be seen from the table, the UV-protective films containing immobilized anthocyanins prepared from the polyethyleneamine-co-methyl methacrylate (2) hydroxyethyl ester copolymer have oxygen and nitrogen permeability of 7.2 × 10⁻⁶, respectively. -16 cm 3 ·cm·cm -2 ·s -1 ·Pa -1 and 2.94×10 -16 cm 3 ·cm·cm -2 ·s -1 ·Pa -1 However, after anthocyanins are reactively linked to polymer molecular chains, the permeability of the membrane material to oxygen and nitrogen is significantly reduced, exhibiting the ability to block gases.

[0047] Table 1. Test results of oxygen and nitrogen permeability for each embodiment.

[0048] The UV-blocking films containing immobilized anthocyanins prepared in Examples 1-7 and the films prepared in Comparative Examples 1-2 were used as packaging materials, and the UV blocking rate of the packaging films was tested using a UV-Vis spectrophotometer. The UV blocking ability test results of the films prepared in Examples 1-7 and Comparative Examples 1-2 after initial film formation and storage for 10 days are as follows: Figure 1 As shown. By Figure 1It can be seen that, with the change of time, the UV blocking ability of the film prepared in Comparative Example 1 remained basically unchanged before and after 10 days of use, and the UV blocking rate was relatively low; the UV blocking rate of the film prepared in Comparative Example 2 decreased from the initial 95.2% to 45.2%; for the UV-protective films containing immobilized anthocyanins prepared in Examples 1 to 7, the UV blocking rate of the film material remained basically unchanged after 10 days of storage, indicating that the UV-protective films containing immobilized anthocyanins prepared by this method have good UV blocking ability and stability in use.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A method for preparing an immobilized anthocyanin UV-protective film, characterized in that, Includes the following steps: Anthocyanins and a binder were added to a solution of polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer to obtain a blend solution; The blend solution is heated to react, and the reaction product is added to a non-solvent phase to precipitate a solid product; The solid product is dried and then dissolved in water to obtain a casting solution. The casting solution was coated and dried to obtain a UV-protective film containing immobilized anthocyanins.

2. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The mass ratio of the polyethyleneamine-co-methacrylic acid (2) hydroxyethyl ester copolymer, anthocyanin and binder is 20:(0.1~0.5):(2~5).

3. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The temperature at which the blend solution is heated is 80℃~120℃.

4. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The binder includes one or more of 1,2-dichloroethane, 1,2-dibromoethane, 1,2-difluoroethane, 1,3-dichloropropane, 1,3-dibromopropane, 1,3-difluoropropane, 1,4-dichlorobutane, 1,4-dibromobutane, or 1,4-difluorobutane.

5. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The non-solvent phase is one of methanol, diethyl ether, or acetone.

6. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The concentration of the casting solution is 2% to 15%.

7. The method for preparing an UV-protective film containing immobilized anthocyanins according to claim 1, characterized in that, The solid product is dried at a temperature of 60~100℃; the casting solution is dried at a temperature of 50~100℃ after coating treatment.

8. A UV-protective film for immobilized anthocyanins, characterized in that, The UV-protective film containing immobilized anthocyanins is prepared according to any one of claims 1-7.

9. The UV-protective film containing immobilized anthocyanins according to claim 8, characterized in that, The thickness of the UV-protective film is 3~300um.

10. The UV-protective film containing immobilized anthocyanins as described in claim 9 is used in the packaging of food and medicine.

Images